named from the fact that during the early months of
summer water falls constantly in the form of a light shower; but it
drips at all times, and in consequence there is an opportunity to study
the active process of formation of one of the deposits which is very
abundant in Wind Cave and considered the most perplexing. This is the
pop-corn, and the theories of its origin have been steadily rejected at
Wind Cave because of a doubt being entertained as to whether it has been
deposited under water or by drippings. Here in Rainy Chamber it is fully
explained. Near the center of the room the fallen masses are heavily
crystallized, much of the groundwork being fine box work and the
crystals in perfect condition. On these crystals the pop-corn is being
formed, and specimens can be seen in all stages of development, from the
beginning to an approximate degree of finish; and whatever the position
it occupies on the receiving surface, either on top, underneath, or on a
side exposure, it always maintains the same relative position as growing
plants on the mundane sphere. The water falling on the upper surface in
scattering drops forms myriads of minute stalagmites; on side positions
the falling drop first strikes the point exposed to its line of descent
and then spreads. The scant moisture slowly makes its way down sloping
sides and shelving edges, leaving on each small irregularity a tiny
portion of its volume, to deposit an infinitely small charge of solid
substance, and the balance finally hangs in moisture less than drops on
the growing grains of the under surface.

Pop-corn, therefore, is the globular aragonite of the stalagmitic
variety. A small specimen from Rainy Chamber, placed beside one of the
same color from Wind Cave, shows them to be absolutely alike.

Rainy Chamber is the room in which the bones of the three-toed horse,
already referred to, were found, but their presence has not yet been
explained; therefore the case is open to conjecture and several
theories may be advanced and their values considered. The first question
when such a discovery is made, is whether the living animal was possibly
a cave-dweller; which, as the horse was not, is quickly disposed of and
attention turned to the next, the possibility of a carniverous animal
having carried his prey into the dark recesses of the cave in order that
the enjoyment of his dinner might be undisturbed. This theory is equally
unavailable by reason of the topographical